Effective isolation and collection of rare cells from a heterogeneous cell population remains of high interest, due to the increasing demand for isolated cell populations for use in disease diagnosis and treatment, e.g. gene therapy, as well as for basic scientific research. For example, pathologically changed cells, such as cancerous cells, can be separated from a larger normal cell population, and the cleaned cell populations may then be transplanted back into the patient.
Cell separation is a rapidly growing area of biomedical and clinical development, and improved methods of separating a desired cell subset from a complex population will permit a broader study and use of cells that have relatively uniform and defined characteristics. Cell separation is also widely used in research, e.g. to determine the effect of a drug or treatment on a targeted cell population, to investigate biological pathways, to isolate and study transformed or otherwise modified cell populations; etc. Present clinical uses include, for example, the isolation of hematopoietic stem cells for reconstitution of blood cells, particularly in combination with ablative chemo- and radiation therapy.
Published U.S. Patent Application No. 2004/038315 attaches releasable linkers to the interior luminal surfaces of capillary tubing, with the desired bound cells subsequently being released via a cleavage reagent and recovered. U.S. Published Patent Application No. 2002/132316 uses microchannel devices to separate cell populations through the use of a moving optical gradient field. U.S. Pat. No. 6,074,827 discloses the use of microfluidic devices that are constructed to have “enrichment channels” wherein electrophoresis is used to separate and identify particular nucleic acids from samples. Also mentioned is the optional use of antibodies or other binding fragments to retain a desired target biomaterial. U.S. Pat. No. 6,432,630 discloses a microflow system for guiding the flow of a fluid containing bioparticles through channels where selective deflection is employed, and it indicates that such systems may be used to separate fetal cells from maternal blood samples.
U.S. Pat. No. 6,454,924 discloses microfluidic devices wherein analyte-containing liquids are caused to flow generally downward past sample surfaces disposed atop upstanding pillars on which capture agents are attached, with the side surfaces of such pillars having been rendered hydrophobic so as to facilitate flow in channels that they define.
K. Takahashi et al., J. Nanobiotechnology, 2, 5 (13 Jun. 2004) (6 pp) disclose on-chip cell sorting systems wherein multiple microfluidic inlet passageways lead to a central cell-sorting region fashioned in a PDMS plate (made in a master mold created in photoresist epoxy resin) that is bonded to a glass plate. Agar gel electrodes are provided in the PDMS plate which facilitate the separation of undesired cells by the application of electrostatic forces that direct these cells into a parallel, continuous waste stream of buffer, during their flow through a short, cell-sorting region of confluence. A pre-filter which uses posts to physically trap large dust particles is also shown. Published International Application WO 2004/029221 discloses a similarly constructed microfluidic device that can be used for cell separation, such as separating fetal RBCs from maternal blood by selective lysis of maternal RBCs. A sample that contains cells may be introduced into a microfluidic channel device which separates whole cells; it contains a plurality of cylindrical obstacles, with the surfaces of the obstacles having binding moieties, e.g., antibodies, suitably coupled thereto, which moieties will bind to cells in the sample. U.S. Pat. No. 5,637,469 discloses microfluidic devices having a plurality of channels of a depth of 100 microns or less wherein binding moieties, such as antibodies, are immobilized on surfaces to capture biomolecules of interest which can be analyzed in situ. U.S. Pat. No. 5,147,607 teaches the use of devices for carrying out immunoassays, such as sandwich assays, where antibodies are mobilized in microchannels. A recessed area can be provided in the microchannel that contains a group of protrusions which extend upward from the bottom surface of the channel and to which the antibodies are immobilized.
The foregoing, briefly described references provide evidence that there is continuing searching for improved separation methods for isolating cells or other biomaterials from bodily fluids or the like.